1.1.5 Size & Mass of Atoms

• Which particles within an atom have a relative mass of 1?

  Protons and neutrons.
• Almost the whole mass of an atom is concentrated where?

  The nucleus.
• How is the size of an atom determined?

  Atomic size is determined by the distance between the nucleus and the outermost electron shell.
• Electrons have virtually no what?

  Mass.
• What does the atomic number tell you?

  The number of protons in an atom.
• What does the mass number tell you?

  The total number of protons and neutrons in an atom's nucleus.
• How do you work out how many neutrons are in an atom?

  Mass number - atomic number.
• What is the radius of an atom?

  0.1 nanometres.
• What are isotopes?

  Isotopes are atoms of the same element that have different numbers of neutrons.